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Phylum Cnidaria > Class Anthozoa > Subclass Zoantharia/Hexacorallia > Order Zoanthidea
Broad zoanthid
Palythoa mutuki

Family Zonathidae
updated Dec 2019

if you learn only 3 things about them ...
They look like tiny sea anemones with long bodies.
Some may be highly toxic. Don't touch them!
They are small and may retract at low tide. Don't step on them!

Where seen? Like a cluster of little brown anemones, this animal is often seen on many of our shores. On coral rubble and among seagrasses in large seagrass meadows.

Features: Colonies generally 5-10cm, each polyp about 1-2cm in diameter with a wide oral disk on a long stout body column. This zoanthid incorporates sand in its body so the body column feels rough to the touch. The wide oral disk has furrows that radiate from the mouth to the edge of the disk. Sometimes with one white furrow so the disk appears to have one split. Relatively short tapered tentacles.

Labrador, Jul 05

Oral disk has furrows.

Long body column that is
rough to the touch.
Labrador, Jun 08
The polyps are not embedded in a thick common tissue but are joined to one another at the base by underground stems (called stolons).The long body column raises the oral disk above the common tissue. Broad zoanthids can multiply by budding. They are found in small clumps of a few to many individuals. Body column usually beige or brown, oral disk usually brown, sometimes shades of green or bright blue.

Some species of broad zoanthids have been recorded to contain the highly toxic palytoxin.

Compared to button zoanthids (Zoanthus sp.), broad zoanthids are generally found in smaller clusters with fewer individuals, although large mounds of them are sometimes seen.

Sometimes confused with sponges, ascidians and other blob-like animals. Here's more on how to tell apart blob-like animals.

What does it eat? Some species are said to capture and eat large prey, rapidly enclosing and swallowing them the way sea anemones do. But this has not been observed in our zoanthids.

At low tide with their tentacles retracted
they look like a clump of sausages.
Chek Jawa, Aug 05

Sisters Island, Jul 06

Kusu Island, Mar 05

Tuas, Aug 09

Pulau Semakau, Aug 11

Species are difficult to positively identify without close examination.
On this website, they are grouped by external features for convenience of display.

Broad zoanthids on Singapore shores
On wildsingapore flickr

Other sightings on Singapore shores

Pulau Pawai, Dec 09

Pulau Sudong, Dec 09

Pulau Salu, Jun 10

Pulau Salu, Jun 10

Pulau Salu, Aug 10

Pulau Salu, Aug 10

Terumbu Berkas, Jan 10

Pulau Berkas, May 10

Pulau Senang, Jun 10

Pulau Biola, Dec 09

Pulau Biola, Dec 09

With grateful thanks to Dr James Reimer of JAMSTEC (Japan Agency for Marine-Earth Science and Technology) for identification of the zoanthids.

  • Borneman, Eric H. 2001. Aquarium Corals: Selection, Husbandry and Natural History T.F. H Publications. 464 pp
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